When is it my time?

So I’m a 66 year old widow raising  2 granddaughters ages 14 and 7 and a great niece age 14.  My older granddaughter who is 20 and my 58 year old sister also live here.  I’ve not really ever had time to be lonely since my husband passed 13 years ago. My son was here briefly, but it wasn’t long before he moved out.  Then my daughter and her family moved in for about 2 months before she and her significant other found a house.  I think it was less than a year after they moved that I became a relative placement for my great nephew and niece who had been removed from their mother’s care.  It was only supposed to be for 6 months.  I didn’t know these kiddos as well as  my youngest sister did so I asked her to move in with me to help.  She had already bonded with them before they were taken from their mom,  so I thought she could help make the transition for these small children easier.  After all, they were only 3 and  2 years old.  All I could think about was how scared I would be if I was taken away from my parents and sent to live with someone I barely knew.. Nearly 13 years later they are still in my care, but my nephew who is now 15 decided he wanted to try living with his grandmother and mother again.  There is an entire story behind that, but he and I have always had a fairly good relationship.  I think it has more to do with the fact that he worries about his mother and grandmother which he has done since he was very small.   He tried to move out there enough times that this time I decided to let him.  I’m still not sure how good a decision that was and it’s been 9 months.  His sister is the more difficult child though.  She thinks because she’s 14 now that she can make all of her own decisions including things like going to stay with a friend I’ve never met without asking permission. She asked me last night if she could go stay with her mom this weekend and became quite angry when I told her I wanted her schoolwork done and turned in before she went.  It got to the point where I had to ask for her phone because she was refusing to follow direction.  She was not willing to turn the phone over so I had to wrestle her for it. That was fun!  I don’t enjoy these arguments.  She knows what my expectations are, but chooses to ignore them. She tried every excuse in the book to get the phone back last night, but I didn’t give in.  Eventually she calmed down. She didn’t get her phone back until I got home from work tonight.  So far she’s been cooperative.  She actually sat with me and worked on her schoolwork this evening.  I’m sure there will be more of these situations, and I may have to use the same strategy again, but she’s still a kid and needs the structure I’m trying to provide.